It looks like pip install looks at
<http://pypi.python.org/pypi/PySide/>, specifically the "Download URL"
link: <http://www.pyside.org/files/>. The latest version of PySide is
available under the wrong name: pyside-qt4.7+1.0.5.tar.bz2, which pip
doesn't know to use. The latest source distribution under the proper
name is pyside-0.1.4.5.tar.bz2, which has a timestamp of 2009-08-19. It
tries to use it and fails.
Solution: pyside-qt4.7+1.0.5.tar.bz2 should be pyside+1.0.5.tar.bz2, or PyPI
package should be PySide-QT4.7.

speaking as a 'user' of pyside, i say the bug IS valid.
but, it is, and always has been, a pyside maintainer issue.
pip uses pypi as its 'source'. pypi is a good(?) means to advertise python
'packages' such as pyside. as it currently stands, any
python/pypi/pip/easy_install user who sees pyside and wants to *easy* install
it will have the same irritating, misleading installation failure, with no idea
of what to do next, except report it to pyside as a pyside bug.
if pyside cannot install that way, why is it in pypi, except for invalid
historical reasons? at least there should be some mention that it cannot be
installed in the 'normal' easy ways. or just move the obsolete source tar files
off of the pyside download page (or tell pypi to look at a dummy page or pkg)
and let pypi complain to the user that it cannot find the package. at which
time maybe they'll ask the pyside maintainers what they should do...
$ pip install dummypyside
Downloading/unpacking dummypyside
Could not find any downloads that satisfy the requirement dummypyside
No distributions at all found for dummypyside

For now installation with easy_install (not PIP) is supported only on windows.
This will work without problems in windows:
>> easy_install PySide
On other platform it will not work simply becasue the binaries compatible with
Setuptools/easy_install were newer created and uploaded to PyPI.
I have plans to add support for building the binaries with my scripts also on
Linux (I'm using Ubuntu). But still it will be available only as source
distribution. It means that easy_install (or PIP) will be able to download the
distribution from PyPI but the binaries will be build on your system (the
process of downloading the source and build of binaries will be handled
transparently by PIP/easy_install). I'm affraid that pre-build binary
distributions will never be available for Linux on PyPI.

Ok, I'm marking this bug as WONTFIX, as PyPi install isn't supported by us, it
was brought to live by community efforts, so probably no one from the core dev
team will take a look at it :-/
In other words, let's try to keep on bugzilla only things that can be fixed by
commits on PySide github repositories with few exceptions. Anyway thanks very
much for the report.